Norwegians who started using snus before age 16 were more likely to become cigarette smokers than those who started using snus later in life, according to a new study.

Snus is moist smokeless tobacco developed in Sweden. It’s contained in a small pouch, and unlike regular chewing tobacco, it doesn’t make the user spit.

Research suggests snus has lower levels of chemicals called nitrosamines than cigarettes and may be less harmful.

In Norway, snus has become a smoking cessation aid and most older snus users are former smokers.

But snus is also becoming increasingly popular among young Norwegian adults, many of whom have not smoked cigarettes. And although research is divided, the current thinking is that snus use reduces the likelihood of taking up smoking.

The authors of the new study wanted to know more about when people start using snus, to see if that ties into whether they also begin smoking cigarettes.

“I already knew about the research investigating associations between snus use and later smoking, but discovered that snus debut age had not been mentioned in that research,” Ingeborg Lund told Reuters Health in an email.

Lund is a researcher with the Norwegian Institute for Alcohol and Drug Research – SIRUS, in Oslo. She and her colleague Janne Scheffels published their study in Nicotine and Tobacco Research.

The researchers analyzed surveys of Norwegian teenagers and adults conducted from 2005 to 2011.

Out of 8,313 people, 409 were long-term snus users who had started using snus before cigarettes or never used cigarettes. Of the snus users, 30 percent were long-term smokers.

Just over one third of the snus users started using snus before age 16. The researchers discovered those participants had two to three times the odds of becoming lifetime smokers, compared to people who began using snus after age 16.

They also found that early snus users had about the same rate of cigarette smoking as non-snus users. About 23 percent of early snus users were current smokers at the time of the survey, compared to only six percent of people who started using snus when they were older.

“Snus use seems to protect against smoking if the snus debut does not happen too early during adolescence,” Lund said.

She said it’s particularly important to keep teenagers tobacco-free until they are at least 16 years old.

“At younger ages, even if they start with a low risk product such as snus, there is a high risk that they will switch to – or add – other high-risk products, such as cigarettes,” she said. “This risk is reduced when they grow older.”

Since snus use is much less common in other countries, Lund said she doesn’t know if these results can be generalized outside of Norway and Sweden.

Lucy Popova, from the Center for Tobacco Control Research and Education at the University of California, San Francisco, told Reuters Health the new study was “interesting.” She was not involved in the research.

“Earlier initiation of snus basically makes it a gateway to tobacco use, to cigarette use in the future,” she said.

Popova explained that traditional Swedish snus is less dangerous than cigarettes.

“But it’s not harm-free, and (what) is really bad is when people start using both products because of increased rates of cardiovascular disease, pancreatic cancers and other problems,” she said.

Snus is fairly new to the U.S., and Popova said the version made in the U.S. isn’t like the traditional Swedish product.

“A research study found that it’s different from the traditional low-nitrosamine snus in Sweden – it’s not necessarily going to be as low-harm,” she said.

Popova is concerned with heavy promotion for smokeless tobacco products like snus.

“There’s been a lot of studies showing that more advertisement for tobacco products makes it more likely that children will use tobacco products,” she said, “and it’s important to keep youth tobacco-free as long as possible.”